Ore conditioning process



Dec. l2, 193?, G. J. HoLT ET Al.

ORE CONDITIONING PROCESS Filed May 2l, 1930 70 727/1 was /Ja/w Patented Dec. 12, 1933 ORE CONDITIONING PROCESS Grover J. Holt, Crosby, Nashwauk, Amel E.

Arthur K. Knickerbocker, St. Paul, Minn., by Francis Minn., Vspecial administrator Richard 0. Hocking, Matson, 'Hibbingg and deceased, late of D. Butler, St. Paul,

Application May 21, 1930. Serial No. 454,398

3 Claims.

This invention relates in general to the treat- 'ment of ore, and more particularly has reference' to processes for the treatment of ore to remove' impurities therefrom.

Ore such as that containing ferrous metals 5 when mined, contains a relatively large percentage of impurities. Itwill be appreciated that to directly treat ore containing a large quantity of impurities to obtain the metal therefrom, would be highly uneconomical, and would result in inefllcient operation of the process for obtaining the metal from the ore. Theproblems of removing the impurities such as silica from the crude ore prior to treatment of the ore to obtain the metal therefrom, has been recognized, and many processes and apparatus have been developed in an attempt to overcome the difficulties.

In spite of the improvements made in the prior art, considerable amounts of ore are discardedv 4and Wasted because of their high silica contents,

it being more economical to discard the ore than to attempt to treat the ore with the processes known, to obtain a product which could be properly treated to obtain the metal therefrom. Most of the developments in the art of conditioning ore preparatory to the treatment for separating metal therefrom, have been directed to improvements in separate process steps and apparatus for carrying the same into eiect so as to obtain a maximum yield of concentrates having low percentages of impurities. As yet, no process has been developed which is adequate for eifectively and efficiently separating the possible maximum amount of silica from ore. Appar-- ently, any further improvement in the individual conditioning steps would not result in any better results as to the percentage of concentrated ore obtained from the crude material.

Further treatment of the concentrates obtained from certain conditioning steps in the process of removing the impurities from ore have been attempted, but at present no radical -improvements in the total results have been obtained.

A primary object of this invention is to provide a process for the treatment of crude ore whereby a maximum percentage of the substantially pure ore is obtained.

Another object of the invention is the provision of an ore concentrating method wherein raw material having substantially low metallic ore content may be conditioned so as to remove the maximum amount of impurities therefrom.

Yet another object of this invention is to devise a process of treating crude ore to reduce the silica content, vinvolving desliming the ore prior to classification and 'subjecting the slime to further treatment to increase the yield of concentrates.

A further object of this invention is to provide a method of treating manganiferous ores to increase the relative iron and manganese content in an economical and efficient manner.

'Still another object of this invention is to provide a method for treating ores which are nonmerchantable so as to increase the ore content to apoint so that the same may be used to advantage.

With these and other objects in view which may appear incidentl to the present improvements, the invention' consists in the steps and 70 combination of steps hereinafter set forth, with the understanding-that it is, within the scope of the present invention to vary the procedure herein set forth and the several steps, Without departing from the spirit of the invention or the scope of the appended claims.

Inaccordance with the present invention, ore to be conditioned is reduced to a size most susceptible to the treatment to be given. After being reduced to the proper size, the ore undergoing treatment is deslimed, scalped, and classified. The classified ore may be concentrated in any suitable manner, the middlings obtained being mixed with the ore undergoing treatment. Slimesresulting from various stages oftreatment of the ore may be treated to increase the yield of concentrates.

In order to more clearly set forth the procedure and the several steps involved in the present invention, there is shown in the accompanying drawing, an outline of the process to be hereinafter described.

In the drawing:

The single `figure is a diagrammatic representation or flow sheet of the process as carried out in accordance with the present invention.

When ore is treated in accordance with the present invention, the crude ore may be passed through a grizzly 1, having openings varying from 2 to 4" in size. This step tends to separate the workable ore from the large fragmentswhich could not properly be handled in the subsequent size reducing apparatus. It of course should be obvious that the size of the openings in the grizzly may be other than those specified, depending upon the particular treatment to which the ore is to be subjected, and upon the type of ore being treated. The oversize from this grizzly may be run through a Crusher to reduce it to the proper size and then fed back with the undersize, if desired.

After separating the workable fragments of ore from the extra large sizes, the workable portions are passed through a size reducing device 2, which may comprise rolls or other suitable reducing elements. The crushed ore from the rolls 2 is then passed to a sizing apparatus 3, which is shown to be a vibrating screen having 1A" openings. The size of the openings in this screen depend, of course, upon the subsequent treatment to which the ore is to be subjected and also upon the type of ore undergoing treatment.

It will also be appreciated that screens or sizing apparatus other than of the type mentioned -may be employed to advantage. The material passing through the screen or separating device 3 is passed on for further treatment,` and the oversize is returned to the size reducing device 2, to be further reduced in size, so that the same may pass through the apertures in the screen or sizing device 3.

The undersize from the separating device 3 is passed on to another separating device 4, adapted to make a finer separation of the material. For the treatment to be hereinafter described, it has been found that material of the size approximateing eight mesh or under is advantageous. The oversize from the separating device 4 may be again crushed in any suitable manner such as by the rolls 5 and then returned to the vibrating screen or other separating device 4 for further separation. While it has been stated that the material may be used to advantage when it has been passed through an eight mesh screen, it should be clearly understood that other sizes may be employed, depending upon the subsequent treatment of the ore and the particular type of ore undergoing treatment. It should also be understood that while a specific sizing procedure has been described, that any other method of reducing the ore to the proper size for the subsequent treatment to be hereinafter described may be employed. While in the foregoing description, no mention has been made as tovwhether the crushing is done in the wet or dry state, it should be clearly understood that it is within the concept of the present invention to crush the ore either by the dry method or by the so-called wet method.

If the ore has been crushed dry, water is added thereto after it passes the vibrating screen 4 and the pulp obtained is subjected to the following treatment. Ore of the proper size is subjected to a treatment to remove the slime therefrom. This step may be carried out in any conventional type of desliming device, such as a drag, screw, or bowl type deslimer 6, either type of which is well known in the art. The deslimed ore from the desliming device is then subjected to a scalping treatment which may be carried out in any suitable type of apparatus, such as a scalping screen 'I or any other device suitable for the purpose.

After passing through the deslimer and scalper, the dewatered sands are classified by means of a classifier ,8, of any conventional type. It may be desired to employ a classifier of the hindered setting type, in which the sands are sized into about ten products, to be subsequently treated to concentrate the same.

Material overflowing from the classifier ,will consist mainly of slimes and of sands of less than one hundred mesh. These materials are united with the slimes from the deslimer and may be passed to a stage in which they are subsequently treated to obtain the concentrates therefrom,

which will increase the eiiiciency of the total concentrating operation. This treatment will be hereinafter described in detail.

The sands from the classifier are then fed to concentrating devices 9 such as tables of the Wilfley type, in each of which the sands are divided into substantially three distinct products. As before mentioned, the sands are classified into about ten products and it may be desirable to employ a separate concentrating table for each product.

In the operation of the concentrating tables, the sands from the classifier as hereinbefore mentioned, are separated into three distinguishable products. The first of these products which contains the concentrates will be found to be in a condition suitable for commercial use. There will also be the usual tailings obtained, which may be discardedor subjected to further treatment as desired. Another product may be taken from the concentrating tables 9, which is between the concentrates and the tailings and which is commonly known as middlings.

The middlings obtained from the concentrating tables may be again subjected to the treatment hereinbefore described and again concentrated on the several concentrating tables. In some instances, it may be found to advantage to reduce the first of the middlings prior to retreatment. It has also been found preferable to mix the middlings as obtained from the tables or after grinding with the material undergoing treatment priorv to the desliming action. Thus it will be appreciated that there are in reality only two products obtained from the concentrating tables 9, one of these products being the tailings, and the other the concentrates containing the originalconcentrates and the concentrates obtainedA from the recirculating middlings.

The middlings obtained have been described as being returned to the deslimer so that they may again enter the classifier and be fed to the concentrating tables. 'I'his procedure has been found advantageous since the middlings from all the tables are united and must again be sized before being fed to the concentrating tables. Where several mill units are operated, it may be found advantageous to treat the middlings on separate concentrating tables, rather than to increase the load on the tables treating the original ore.

In any event, it will be appreciated that by treating the middlings, additional concentrates can be obtained which will enhance the economy of the process. As hereinbefore mentioned, the slimes resulting from desliming the ore and from classifying the deslimed ore may be further treated to increase the yield of the concentrates from the process. One advantageous method for separating the concentrates from the slimes, and which may be advantageously employed, is the so-called flotation process. When it is desired to employ flotation to separate the concentrates from the slimes, it will be found advisable to first thicken the slimes so as to reduce the bulk of material to be handled. The thickening of the slimes may be carried out in the well known Dorr thickener or other similar and suitable devices.

The thickened pulp passing from the thickening stage 10 may be passed directly to a flotation stage 11, consisting of conventional fiotation cells. In carrying out the flotation reaction reagents such as sodium silicate, sodium carbonate, pine oil and one of the lower fatty acids, such as oleic, stearic or palmitic may be employed to advantage. It is also contemplated to employ other flotation reagents suitable for eiiiciently eifect- 15p ing the flotation reaction. The concentrates from the flotation process may be taken as a finished product or it may be preferable to subject the concenetrates to a second flotation reaction 12. When two flotation stages are employed, the first stage may be considered as the roughing stage and the second stage as the cleaner stage. When the two stages of flotation are employed, the final concentrates may be mixed directly with the concentrates obtained from the concentrating tables 9.

Desirable results may be obtained by subjecting the tailings from the second flotation stage to a second treatment. When the tailings from the second stage'of flotation are to be retreated, it is preferable to mix them with the slimes prior to thickening, so that the same may be subjected to the rough flotation and the cleaner flotation stage 12 to obtain further concentrates therefrom.

The concentrates obtained from the concentrating tables and from the slimes may be mixed and shipped directly as a merchantable product.

To illustrate the effectiveness of the present invention, results from a test run on 100 tons of ore will be given. A crude ore such as obtained from the iron ranges at Minnesota and Michigan was found to contain on analysis, iron 25.3%, manganese 24% and silica 18.6%. Other impurities in the ore were in such small quantities as to be of little effect. After desliming, scalping and classifying, the sands were found to be of a composition containing iron 25.7%, manganese 24.8% and silica 16.8%. Upon analysis of the material passing over the concentrating tables, the rst concentrates amounting to 46.2

tons showed a composition of iron 27%, man-- ganese 28.1% and silica 10.8%. The middlings from the concentrating tables totaling 25.7 tons` contained iron 25.3%, manganese 23.8% and silica 18.6%. Concentrates obtained from the middlings upon retreatment weighed about 18 tons and had a composition consisting of iron 28.1%, manganese 28.2% and silica 9.7%. Tailings from the first concentration of the original ore contained iron 22.1%, manganese 15.6% and silica 33.6%, and the tailings from the middlings after retreatment assayed iron 18.7% manganese 13.5% and silica 40.1%. The first tailings weighed 13.4 tons and the second tailings from middlings weighed 7.7 tons.

Slimes obtained from the desliming and classification of the ore amounted to about 14.7 tons and contained iron 23.7%, manganese 20% and silica 27.4%. After treatment, the concentrates obtained amounting to 5.2 tons consisted of iron 24.4%, manganese 27.1% and silica 14%, Whereas the notation tailings weighed 9.5 tons and assayed iron 22.4%, manganese 14.8% and silica 37.8%. From the foregoing values, it will be appreciated that ore when treated in accordance with the present invention may be advantageously and economically separated, so as to produce a merchantable product.

It may be desirable to further treat the concentrates obtained prior to shipment. This treatment may consist in dewatering the concentrates. In some instances, it may be found advantageous to sinter the concentrates for convenience in handling. It will be appreciated from the foregoing disclosure that the present invention provides a method for treating crude unmerchantable ore, so as to convert the same to a merchantable product having a relatively high percentage of metallic ore.

While we have shown and described the preferred embodiment of our invention, We Wish it to be understood that we do not confine ourselves to the precise details of procedure herein set forth, by Way of illustration, as it is apparent that many changes and variations may be made therein by those skilled in the art, Without departing from the spirit of the invention, or exceeding the scope of the appended claims.

We claim:

1. In a method of conditioning ores, the steps of reducing the ore to a determined maximum size, subjecting the ore to a desliming treatment, classifying the deslimed product, thickening the slimes obtained from the desliming treatment and the classification, subjecting the thickened slirnes to fiotation, subjecting the concentrates from the flotation reaction to a second flotation and mixing the tailings from the second flotation step with the'slimes prior to thickening.

2. A method of treating ore comprising desliming a crushed ore, thickening the slime, subjecting the thickened slime to a flotation treatment, subjecting the concentrates from the flotation treatment to a second flotation step to increase the relative content of the desired constituents of the ore, and mixing the tailings from the second flotation step with the slime undergoing treatment prior to thickening.

3. A method of treating ores to recover the valuable' constituents comprising crushing the ore, desliming the crushed ore, classifying the crushed ore into a plurality of sand products and a slime, tfbling in separate lots each of the several sand products, returning directly to the material undergoing treatment prior to the desliming step the tabled middlings, and concentrating by flotation the slimes from the desliming and classifying steps.

GROVER J. HOLT. RICHARD O. HOCKING. AMEL E. MATSON. FRANCIS D. BUTLER, Special Administrator of the Estate of Arthur K.

Knickerbocker, also known as A. K. Knickerbocker. 

